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We model the distance, extinction, and magnitude probability distributions of a successful Galactic core-collapse supernova (ccSN), its shock breakout radiation, and its massive star progenitor. We find, at very high probability (~100%), that the next Galactic SN will easily be detectable in the near-IR and that near-IR photometry of the progenitor star very likely (~92%) already exists in the 2MASS survey. Most ccSNe (~98%) will be easily observed in the optical, but a significant fraction (~43%) will lack observations of the progenitor due to a combination of survey sensitivity and confusion. If neutrino detection experiments can quickly disseminate a likely position (~3 deg), we show that a modestly priced IR camera system can probably detect the shock breakout radiation pulse even in daytime (~64% for the cheapest design). Neutrino experiments should seriously consider adding such systems, both for their scientific return and as an added and internal layer of protection against false triggers. We find that shock breakouts from failed ccSNe of red supergiants may be more observable than those of successful SNe. We review the process by which neutrinos from a Galactic ccSN would be detected and announced. We provide new information on the EGADS system and its potential for providing instant neutrino alerts. We also discuss the distance, extinction, and magnitude probability distributions for the next Galactic Type Ia SN. Based on our modeled observability, we find a Galactic ccSN rate of 3.2 (+7.3/-2.6) per century and a Galactic Type Ia SN rate of 1.4 (+1.4/-0.8) per century for a total Galactic SN rate of 4.6 (+7.4/-2.7) per century is needed to account for the SNe observed over the last millennium.
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The next core-collapse supernova in our Galaxy will be a spectacular event, with some $10^4$ neutrino detections in total expected among several detectors. This data will allow unprecedented tests of neutrino properties and new opportunities in astrophysics. In this paper, I focus on two main topics: (1) Measurement of the $ u_mu$ and $ u_tau$ masses by time-of-flight, with an emphasis on introducing as little supernova model dependence as possible, and (2) Methods for locating a supernova by its neutrinos in advance of the light, which may allow improved astronomical observations. In the latter, I also discuss the recent result that the positrons from $bar{ u}_e + p to e^+ + n$ are not isotropically emitted, as commonly thought.
The origin of cosmic rays holds still many mysteries hundred years after they were first discovered. Supernova remnants have for long been the most likely sources of Galactic cosmic rays. I discuss here some recent evidence that suggests that supernova remnants can indeed efficiently accelerate cosmic rays. For this conference devoted to the Astronomical Institute Utrecht I put the emphasis on work that was done in my group, but placed in a broader context: efficient cosmic-ray acceleration and the im- plications for cosmic-ray escape, synchrotron radiation and the evidence for magnetic- field amplification, potential X-ray synchrotron emission from cosmic-ray precursors, and I conclude with the implications of cosmic-ray escape for a Type Ia remnant like Tycho and a core-collapse remnant like Cas A.
The late-time evolution of the neutrino event rate from supernovae is evaluated for Super-Kamiokande using simulated results of proto-neutron star (PNS) cooling. In the present work we extend the result of Suwa et al. (2019) [arXiv:1904.09996], which studied the dependence on the PNS mass, but focus on the impact of the nuclear equation of state (EOS). We find that the neutrino event rate depends on both the high-density and low-density EOS, where the former determines the radius of the PNS and the latter affects its surface temperature. Based on the present evaluation of the neutrino event rate we propose a new analysis method to extract the time variability of the neutrino average energy taking into account the statistical error in the observation.
Active galactic nuclei (AGN) are prominent environments for stellar capture, growth and formation. These environments may catalyze stellar mergers and explosive transients, such as thermonuclear and core-collapse supernovae (SNe). SN explosions in AGN discs generate strong shocks, leading to unique observable signatures. We develop an analytical model which follows the evolution of the shock propagating in the disc until it eventually breaks out. We derive the peak luminosity, bolometric lightcurve, and breakout time. The peak luminosities may exceed $10^{45}$ erg s$^{-1}$ and last from hours to days. The brightest explosions occur in regions of reduced density; either off-plane, or in discs around low-mass central black holes ($sim 10^6 M_odot$), or in starved subluminous AGNs. Explosions in the latter two sites are easier to observe due to a reduced AGN background luminosity. We perform suites of 1D Lagrangian radiative hydrodynamics SNEC code simulations to validate our results and obtain the luminosity in different bands, and 2D axisymmetric Eulerian hydrodynamics code HORMONE simulations to study the morphology of the ejecta and its deviation from spherical symmetry. The observed signature is expected to be a bright blue, UV, or X-ray flare on top of the AGN luminosity from the initial shock breakout, while the subsequent red part of the lightcurve will largely be unobservable. We estimate the upper limit for the total event rate to be $mathcal{R}lesssim 100 rm yr^{-1} Gpc^{-3}$ for optimal conditions and discuss the large uncertainties in this estimate. Future high-cadence transient searches may reveal these events. Some existing tidal disruption event candidates may originate from AGN supernovae.
Supernova neutrinos are crucially important to probe the final phases of massive star evolution. As is well known from observations of SN1987A, neutrinos provide information on the physical conditions responsible for neutron star formation and on the supernova explosion mechanism. However, there is still no complete understanding of the long-term evolution of neutrino emission in supernova explosions, although there are a number of modern simulations of neutrino radiation hydrodynamics, which study neutrino emission at times less than one second after the bounce. In the present work we systematically calculate the number of neutrinos that can be observed in Super-Kamiokande over periods longer than ten seconds using the database of Nakazato et al. (2013) anticipating that neutrinos from a Galactic supernova can be detected for several tens of seconds. We find that for a supernova at a distance of 10 kpc, neutrinos remain observable for longer than 30 s for a low-mass neutron star ($1.20M_odot$ gravitational mass) and even longer than 100 s for a high-mass neutron star ($2.05M_odot$). These scenarios are much longer than the observations of SN1987A and longer than the duration of existing numerical simulations. We propose a new analysis method based on the cumulative neutrino event distribution as a function of reverse time from the last observed event, as a useful probe of the neutron star mass. Our result demonstrates the importance of complete modeling of neutrino light curves in order to extract physical quantities essential for understanding supernova explosion mechanisms, such as the mass and radius of the resulting neutron star.
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